Field of the Invention
The present invention relates to a waveguide filter, and in particular, relates to a waveguide filter utilized in a satellite antenna.
Description of the Related Art
Conventional waveguide filters, such as Tapered Chebyshev function stub filters and Tapered Zolotarev function stub filters, have large dimensions due to impedance matching requirements.
The waveguide filters are commonly formed by molding. FIG. 1A shows a conventional waveguide filter 1, which has an upper structure 10 and a lower structure 20. The upper structure 10 has an upper rib 11, and the lower structure 20 has a lower rib 21. In the manufacturing process of the waveguide filter 1, the upper structure 10 and the lower structure 20 are formed by molding separately. In the assembled waveguide filter 1, a junction line 30 is kept away from the upper rib 11 and the lower rib 21 to assure surface smoothness of the upper rib 11 and the lower rib 21, and to prevent noise from being generated due to an uneven surface of the upper rib 11 and the lower rib 21.
However, if the junction line 30 passes through the ribs, the surfaces of the ribs are uneven due to manufacturing discrepancies, and noise is therefore generated. With reference to FIG. 1B, if the junction line 30′ passes through the rib 11, the rib 11 is divided into a section 12 and a section 13, and an uneven portion 14 is formed between the section 12 and the section 13 due to the manufacturing discrepancies. Any uneven portion in the waveguide filter changes the impedance matching thereof. Thus, it is important that the junction line is kept away from the ribs or other important filtering structures.